1. Field of the Invention
The present invention relates to an optical disc device and, more particularly, is suitably applied to an optical disc device for performing recording and reproduction of data on and from an optical disc.
2. Description of the Related Art
Optical disc devices perform seek control using a traverse signal formed by binarizing a tracking error signal outputted from an optical pickup.
In detail, when an optical pickup is placed over a groove, a tracking error signal attains the lowest signal level, so that traverse signals, in which a “Hi” period and a “Lo” period appears alternately, can be obtained by properly setting a threshold, thereby enabling the moving speed of the optical pickup and the number of traversed tracks (seek amount) to be detected based on the traverse signals.
However, there is a case where the amplitude of a tracking error signal is reduced by various reasons such as a defect of the optical disc and dust sticking thereto. In such a case, the traverse signal continues to be at “Lo” (which is referred to as “signal skip”), so that the optical disc device makes a track count miss, in which the seek amount is erroneously recognized to be too small. Due to this track count miss, the optical pickup overruns the target and the correct address is not obtained at the intended destination track. In this case, the optical disc device generally needs to once return the optical pickup to a predetermined reference position, so as to restart seeking from the reference position, which results in a problem that the performance of the whole optical disc device is decreased.
In order to solve this problem, there has been proposed a signal processing method in which the frequency of the traverse signal is monitored, and when the frequency is remarkably increased or decreased, an abnormality is judged to have occurred, so that the seek is made to be continued by complementing the abnormal part of the traverse signal using a past average value (of several tracks, for example) of the traverse signals (see, for example paragraph 0009-0010 of Japanese Patent Laid-open No. 2003-151147).